Electrostatic actuator and method of controlling the same

Abstract

An electrostatic actuator comprises a movable element having electrodes arranged at given intervals, a stator having driving electrodes wired and arranged in groups at given intervals, and a displacement control unit configured to control displacement of the movable element. The displacement control unit controls the displacement of the movable element by changing a phase difference between a first traveling wave generated in an array of the electrodes by applying a first AC voltage to the electrodes of the movable element, and a second traveling wave generated in an array of the driving electrodes by applying a second AC voltage to the driving electrodes of the stator.

1 . An electrostatic actuator comprising: 
 a movable element having electrodes arranged at given intervals;    a stator having driving electrodes wired and arranged in groups at given intervals; and    a displacement control unit configured to control displacement of the movable element by changing a phase difference between a first traveling wave generated in an array of the electrodes by applying a first AC voltage to the electrodes of the movable element, and a second traveling wave generated in an array of the driving electrodes by applying a second AC voltage to the driving electrodes of the stator.    
   
   
       2 . The electrostatic actuator according to  claim 1 , wherein the displacement control unit controls displacement of the movable element by changing stepwise a relative phase between the first and second AC voltages as a phase offset within 180° of one of positive and negative phases.  
   
   
       3 . The electrostatic actuator according to  claim 1 , further comprising a speed controller which is configured to control the speed of the movable element by changing a frequency difference between the first and second AC voltages.  
   
   
       4 . The electrostatic actuator according to  claim 3 , wherein the displacement control unit changes a phase difference between the first and second traveling waves, after stopping the movable element by the speed controller by making the frequencies of the first and second AC voltages the same.  
   
   
       5 . An electrostatic actuator comprising: 
 a stator having inductive electrodes arranged one of concentrically and substantially parallel to each other, and driving electrodes wired and arranged in groups at given intervals;    a movable element having first and second electrodes interdigitally arranged each other; and    a displacement control unit configured to control displacement of the movable element by changing a phase difference between a first traveling wave generated in an array of the electrodes of the movable element by inducing electric charges to the first and second electrodes of the movable element by applying a first AC voltage to the inductive electrodes of the stator, and a second traveling wave generated in an array of the driving electrodes by applying a second AC voltage to the driving electrodes of the stator.    
   
   
       6 . The electrostatic actuator according to  claim 5 , wherein 
 the movable element is a rotating rotor in which a first electrode consisting of radially spreading comb-like end electrodes, and a second electrode consisting of concentrically arranged comb-like end electrodes are interdigitally arranged each other; and    the stator incorporates two or more inductive electrodes arranged on the circumference of a disk, and driving electrodes wired and arranged in groups with given periodic angles.    
   
   
       7 . The electrostatic actuator according to  claim 6 , wherein the rotor and stator are stacked to be multiple layers taking a common rotation shaft, the rotation torque generated by a plurality of rotors being conveyed through the common rotation shaft.  
   
   
       8 . The electrostatic actuator according to  claim 5 , wherein 
 the movable element is composed of a first electrode having a comb-tooth shape interdigitally arranged to a second electrode having substantially the same shape, and is placed on the internal surface of a cylinder so that the directions of the first and second electrodes are aligned as a straight line; and    the stator is composed of driving electrodes arranged to be aligned with two or more inductive electrodes placed on the straight lines on a cylinder.    
   
   
       9 . The electrostatic actuator according to  claim 5 , wherein 
 the movable element is circumferentially rotating movable element composed of a first electrode having a comb-tooth shape interdigitally arranged to a second electrode having substantially the same shape, and is placed on the internal surface of a cylinder so that the directions of the first and second electrodes are aligned as a circle; and    the stator is composed of driving electrodes arranged to be aligned with the two or more inductive electrodes placed on the circumference of a cylinder.    
   
   
       10 . The electrostatic actuator according to  claim 5 , wherein the displacement control unit controls displacement of the movable element by changing stepwise a relative phase between the first and second AC voltages as a phase offset within 180° of one of positive and negative phases.  
   
   
       11 . The electrostatic actuator according to  claim 5 , further comprising a speed controller which is configured to control the speed of the movable element by changing a frequency difference between the first and second AC voltages.  
   
   
       12 . The electrostatic actuator according to  claim 11 , wherein the displacement control unit changes a phase difference between the first and second traveling waves, after stopping the movable element by the speed controller by making the frequencies of the first and second AC voltages the same.  
   
   
       13 . An electrostatic actuator comprising: 
 a stator having driving electrodes wired and arranged in groups at given intervals;    a movable element having first and second electrodes interdigitally arranged each other; and    a displacement control unit configured to control displacement of the movable element by changing a phase difference between a first traveling wave generated in an array of the electrodes by applying a first AC voltage between the first and second electrodes of the movable element, and a second traveling wave generated in an array of the driving electrodes by applying a second AC voltage to the driving electrodes of the stator.    
   
   
       14 . The electrostatic actuator according to  claim 13 , wherein 
 the movable element is a rotating rotor in which a first electrode consisting of radially spreading comb-like end electrodes is interdigitally arranged to a second electrode consisting of concentrically arranged comb-like end electrodes; and the stator incorporates driving electrodes wired and arranged in groups with given periodic angles.    
   
   
       15 . The electrostatic actuator according to  claim 14 , wherein the rotor and stator are stacked to be multiple layers taking a common rotation shaft, the rotation torque generated by a plurality of rotors being conveyed through the common rotation shaft.  
   
   
       16 . The electrostatic actuator according to  claim 13 , wherein 
 the movable element is composed of a first electrode having a comb-tooth shape interdigitally arranged to a second electrode having substantially the same shape, and is placed on the internal surface of a cylinder so that the directions of the first and second electrodes are aligned as a straight line; and    the stator is composed of driving electrodes arranged to be a straight line.    
   
   
       17 . The electrostatic actuator according to  claim 13 , wherein 
 the movable element is circumferentially rotating movable element composed of a first electrode having a comb-tooth shape and a second electrode having substantially the same shape which are interdigitally arranged each other, and placed on the internal surface of a cylinder so that the directions of the first and second electrodes are aligned as a circle; and    the stator is composed of driving electrodes arranged to be a circumference.    
   
   
       18 . The electrostatic actuator according to  claim 13 , wherein the displacement control unit controls displacement of the movable element by changing stepwise a relative phase between the first and second AC voltages as a phase offset within 180° of one of positive and negative phases.  
   
   
       19 . The electrostatic actuator according to  claim 13 , further comprising a speed controller which is configured to control the speed of the movable element by changing a frequency difference between the first and second AC voltages.  
   
   
       20 . The electrostatic actuator according to  claim 19 , wherein the displacement control unit changes a phase difference between the first and second traveling waves, after stopping the movable element by the speed controller by making the frequencies of the first and second AC voltages the same.  
   
   
       21 . A method of controlling an electrostatic actuator comprising: 
 generating a first traveling wave in an array of electrodes by applying a first AC voltage to the electrodes arranged on a movable element at given intervals;    generating a second traveling wave in an array of driving electrodes by applying a second AC voltage to the driving electrodes arranged on a stator at given intervals; and    controlling displacement of the movable element by changing a phase difference between the first and second traveling waves.    
   
   
       22 . The control method according to  claim 21 , wherein controlling displacement of the movable element includes controlling displacement of the movable element by changing stepwise a relative phase between the first and second AC voltages as a phase offset within 180° of one of positive and negative phases.  
   
   
       23 . The control method according to  claim 21 , further comprising controlling the speed of the movable element by changing a frequency difference between the first and second AC voltages.  
   
   
       24 . The control method according to  claim 23 , wherein controlling displacement of the movable element includes changing a phase difference between the first and second traveling waves, after stopping the movable element by making the frequencies of the first and second AC voltages the same by controlling the speed of the movable element.